Contact lens comprising a violet tint

ABSTRACT

Adding a small quantity of a violet colorant to a contact lens material provides a clear contact lens that has no apparent undesirable yellow tint, such as caused by a UV-absorbing compound. Further, the violet colorant can also be used with a colored lens, in the absence of the handling tint, to mask any undesirable yellow tint, such as that produced by a UV-absorbing compound. The violet colorant will not unacceptably alter the modifying color of the colored lens.

This application is a continuation of application Ser. No. 09/149,413,filed Sep. 8, 1998, now U.S. Pat. No. 6,183,083.

BACKGROUND OF THE INVENTION

Members of the contact lens industry recognize that, on occasion, aconventional clear, colorless contact lens may include a yellow tint.The yellow tint can adversely affect consumer acceptance of the contactlens. The yellow tint can result from improper processing of the contactlens polymer, or from certain ingredients in the lens polymer.Therefore, it is sometimes difficult to predictably avoid the yellowtint in the manufacture of clear, colorless lenses.

Further, due to public concern over the potentially harmful effects ofultraviolet radiation (UV), some contact lens manufacturers have begunto add UV-absorbing compounds to contact lenses. Unfortunately,compounds that absorb UV radiation also tend to impart an undesirableyellow tint to the lenses, if the compounds are present in sufficientamounts to absorb strongly above 380 nm. Therefore, what was once anunpredictable problem may become an unavoidable problem for clear,colorless lenses that contain or are treated with a UV-absorber.

For many clear lenses, the yellow tint is not particularly troublesomebecause manufacturers already add a handling tint to these lenses. Ahandling tint is a color (usually green or blue) that is dispersedevenly throughout the lens or bonded to the lens surface in sufficientamounts to make the contact lens more easily observable for handlingpurposes. Typically, the amount of handling tint added will notsubstantially modify the wearer's eye color or affect the passage oflight through the lens.

In the absence of the regular use of a handling tint, a prudentmanufacturer would, nevertheless, mask a clear, UV-absorbing lens with amore desirable masking tint to hide the undesirable yellow tint impartedby the UV-absorbing compound. Handling tint and masking tints aregenerally made from the same or similar colorants, and in the same orsimilar concentrations. Therefore, for the purposes of the presentdisclosure, they are referred to collectively as masking tints. Inaddition, clear lenses that contain such traditional masking tints arereferred to as tinted, clear lenses.

However, even the use of a traditional masking tint may not adequatelymask the yellow tint for a clear lens. For a thicker lens, such as atoric lens, the traditional masking tint may not adequately hide theyellow color. In this case, adding enough masking tint to hide theyellow tint may also result in a substantial effect on the wearer'sapparent eye color. Further, many clear lens consumers also prefer acolorless lens. For these consumers, the absence of a traditionalhandling tint will only highlight any yellow tint imparted by anUV-absorber or by other sources.

Moreover, in the context of a lens that is used to change the wearer'seye color (a colored lens), the yellow tint poses a substantial problem.In a colored lens, either a section of the lens or the whole lenscontains sufficient color to modify a wearer's eye color (hereinafter“modifying color”). As an example, one can use the lens patented byKnapp in U.S. Pat. No. 4,582,402, which has achieved considerableconsumer acceptance. In the Knapp lens, the modifying color is printedonto the contact lens as a pattern of color elements (generally dots)over the region of the lens that substantially covers the iris. However,the interstices between the color elements, and the other sections ofthe lens (e.g., those that cover the pupil and the sclera) remainessentially clear and colorless (occasionally, a barely visible patternor a small pattern is printed on part of the sclera region).

For such a lens, the presence of a yellow tint, whether or not due tothe addition of a UV-absorber, dramatically reduces its acceptance byconsumers. Efforts to overcome the yellow tint by adding a traditionalmasking tint did not achieve satisfactory results because traditionalmasking tints tend to unacceptably alter the modifying color. Inaddition, efforts to mask the yellow tint in colored lenses did notpredictably alter the appearance of the lens. For example, a coloredlens containing both an UV-absorber and a masking tint will modify thelens appearance in a different way than the same lens that does notcontain the UV-absorber.

Blue or green are the traditional colors for masking tints because theyhave achieved general acceptance by consumers. Although violet pigmentshave been used in other contexts for contact lens (e.g., as a modifyingcolor or part of a modifying color pattern, and for the small, barelyvisible printing on the sclera of a color lens), violet has not beenused as a masking tint. By itself, and at higher concentrations, aviolet masking tint tends to impart a darker appearance to the contactlens. At even higher concentrations, the violet color will adverselymodify the wearer's eye color. Contact lens manufacturers do not believea contact lens that contains such concentrations of violet tint canachieve consumer acceptance.

Nevertheless, it would be desirable, especially in the context of addingan UV-absorbing compound, to formulate a lens wherein the presence ofyellow tint can be effectively masked. It would be especially desirableto mask the yellow tint in a colored lens without adversely altering themodifying colors.

SUMMARY OF THE INVENTION

Surprisingly, addition of a violet colorant to a clear lens in an amountsufficient to mask the effect of the yellow tint will not affectconsumer acceptance, if it is used in small amounts. In one aspect ofthe invention, the violet colorant is used to mask the effect of theyellow tint caused by the presence of an UV-absorber in a clearcolorless lens. In a second aspect of the invention, the violet colorantis combined with a traditional masking tint in a tinted, clear lens tomask the effect of yellow tint caused by the presence of an UV-absorber.In a third aspect, sufficient amounts of the violet tint can be used tomask yellow tint in a colored lens without affecting consumeracceptance, provided the amount used is sufficiently small to avoidaltering the appearance of the lens.

In these lenses, the concentration of violet colorant must be carefullymonitored to avoid noticeably altering the lens appearance. In otherwords, when the amount of violet colorant in the lens is carefullybalanced between an amount sufficient to mask the effect of the yellowtint and an amount that is not substantially noticeable, the violetcolorant can be used for a clear colorless lens, a tinted clear lens, ora colored lens. In such a concentration, the violet colorant can be usedto hide yellow tint caused by the presence of an UV-absorber withoutadversely affecting consumer acceptance of the lens. The resultinglenses, which include the proper amount of violet colorant to mask theyellow tint caused by UV absorbing compounds, are cosmeticallyindistinguishable from a lens without the UV absorber.

DETAILED DESCRIPTION OF THE INVENTION

In the context of this invention, although some terms are referred to inthe singular, it is understood that such references may also encompassthe plural. For example, although color is referred to in the singular,it is understood that some colors comprise many color components.Further, it is understood that a colored lens is used to modify thewearer's eye color, and that eye color, in fact, refers to the color ofthe iris. Furthermore, the term “tint” refers to the even dispersion ofcolorant in the lens. Moreover, all percentages are based on weightpercentages unless otherwise specified. Finally, all references citedherein are incorporated by reference.

It has been found that adding a violet colorant to a contact lens caneffectively hide the presence of an undesirable yellow tint in the lens.Moreover, it is possible to overcome any undesirable appearance normallyassociated with the violet colorant when the amount added issufficiently small to avoid notice by the consumer. For a clear,colorless lens, an amount of violet colorant sufficient to mask theyellow tint may be evenly dispersed in the lens so as to beunnoticeable.

In a similar manner, the amount sufficient to mask the yellow tint canalso be evenly dispersed in a tinted, clear lens. In such a lens, theviolet colorant hides the yellow tint regardless of the thickness of thelens. Moreover, for the tinted, clear lens, the violet colorantconcentration need not be as carefully monitored because the traditionalmasking tints also hide the darker appearance normally associated withthe violet colorant. In combination, the two tints mask the effect ofthe yellow tint and at the same time impart a commercially acceptableappearance to the contact lens.

However, one cannot conclude that a violet colorant will have no effecton a tinted, clear lens. When too much violet colorant is used, acolorless lens that contains both the masking tint and the violet tintwill appear darker than one that contains only the masking tint in adirect comparison. However, without the direct comparison, an averageconsumer will not notice the effect of the violet colorant.

For a colored lens, the violet colorant also effectively hides theyellow tint and/or its adverse effect on the modifying color of thecolored lens. As in the case of the clear, colorless lens, the amount ofviolet colorant used can be monitored carefully so that the consumerdoes not notice it. Further, like the tinted, clear lens, theconcentration of the violet colorant need not be as carefully monitoredas for the clear colorless lenses. At smaller concentrations of violetcolorant, the modifying color effectively produces the illusion that theviolet tinted contact lens does not have the darker appearance normallyassociated with the violet colorant. Once again, in a direct comparison,the ordinary wearer would probably observe that the colored lens withthe violet colorant is darker than the colored lens without the violetcolorant. However, without the direct comparison, the ordinary wearerwould probably not notice the difference. In this manner, the violetcolorant is generally compatible with the modifying color.

It is apparent that determining whether a sufficient amount of violettint, or violet colorant, is present to hide yellow tint, and whetherthe amount of violet colorant is sufficiently small so that it is notreadily apparent to an ordinary observer, requires some experimentation.However, in the context of this invention and the cosmetic contact lensindustry, such determinations through, e.g., focus groups, do notconstitute an undue burden. An amount of violet colorant sufficient tomask yellow tint is an amount that, when added to a lens that otherwisemanifests a yellow tint, prevents the ordinary wearer from noticing theyellow tint. In other words, the ordinary observer would deem the maskedlens to be cosmetically indistinguishable from a lens having neither theyellow tint-causing agent, nor the masking agent. Conversely, asufficiently small amount of violet colorant is one that, without adirect side-by-side comparison with another lens, will not appear to theordinary wearer to have a violet tint.

A UV-absorbing contact lens that is cosmetically indistinguishable froma lens without a UV-absorbing compound may be made in accordance withthis invention. This lens is made by adding a UV-absorbing compound to acontact lens formulation in sufficient amounts that would cause a yellowtint to result in a conventional contact lens formulation; and thenadding a violet colorant to the formulation in sufficient amounts tomask the yellow tint that would otherwise be present without the violetcolorant, such that the contact lens is cosmetically indistinguishablefrom a lens without the UV-absorbing compound. Also, this lens may bemade by adding a UV-absorbing compound to a contact lens formulation inan amount sufficient to cause a yellow tint, adding violet colorant tothe formulation in an amount sufficient to mask the yellow tint causedby the presence of the UV-absorbing compound; and polymerizing theformulation and forming the polymer into a contact lens.

The method also may include titrating the contact lens formulationcontaining the UV-absorbing compound and determining the amount ofviolet colorant added when the yellow tint has been masked. This isparticularly useful when an amount of UV-absorber has been added to theformulation, and the yellow tint is readily apparent. For example, ayellow tint is readily apparent in a contact lens formulation thatincludes more than about 1% by weight dry basis of a UV-absorber such as2-(2′-hydroxy-3′-tert-butyl-5′-(3″-(4′″-vinylbenzoxy)propoxy)phenyl)-5-methoxy-2H-benzotrizole,and the like, which are described more fully in U.S. Pat. No. 5,729,322to Collins and Mulvihill. This yellowish tint may also be apparent whenless amounts of this class of UV-absorbing compound are used.

Generally, however, it is desirable to use at least about 0.9% by dryweight basis of this type of UV-absorber to obtain the desired levels ofUV absorption, depending on the thickness of the lens. Therefore, theuse of carbazole violet in accordance with this invention may bedesirable over a broader range of amounts of UV-asbsorber formanufacturing consistency and efficiency, rather than testing lenses onan individual basis for its yellowish tint.

The practice of this invention is not dependent on the particularcontact lens used, the particular color used, or any particular methodof manufacturing a contact lens. The only important detail is that asmall quantity of a violet colorant can be added to contact lens to maskany undesirable yellow tint that may result from a number of reasons,including the addition of a UV-absorber to the contact lens. Anotherfurther detail is that the amount of violet colorant added is thatsufficient to mask yellow tint, but sufficiently small to avoid noticeby the average consumer. Details such as the formulation and productionof the contact lenses, the formulation and production of the modifyingcolors and the methods of combining the modifying colors with thecontact lenses are known to artisans of the contact lens industry. Thefollowing details are provided to illustrate the invention, and do notlimit the scope of the invention.

The preferred lenses contain modifying colors in the form a pattern ofcolor elements that are dots, as taught in U.S. Pat. Nos. 4,582,402 toKnapp, and 5,414,477 to Jahnke. However, in the context of thisinvention, the dots need not be opaque. For a lens used with a darkcolored iris, the dots are preferably opaque dots. For a lens used witha light colored iris, the dots can be either opaque or non-opaque.

In the present invention, the color elements can be applied to a varietyof contact lenses, on the anterior (away from eye) or posterior (incontact with eye) surface, or formulated within the contact lens. In apreferred lens, the pattern is applied to the anterior surface. On ahard contact lens, the outer periphery of the pattern lies atsubstantially the edge of the contact lens. On a soft contact lens, theouter periphery of the pattern may be surrounded by a non-opaque sclerasection. The preferred contact lenses are disclosed in U.S. Pat. Nos.4,405,773 and 4,668,240 both to Loshaek. Other examples of lenses withcolor modifying elements are disclosed in U.S. Pat. Nos. 4,857,072 and4,963,159 both to Narducy et al., and 5,272,010 to Quinn.

Methods of making contact lenses that have a color pattern are known tothe ordinary artisan. The preferred methods of producing contact lenseshaving the pattern of the present invention are described in U.S. Pat.Nos. 4,582,402 to Knapp, and 5,414,477 to Jahnke. Other examples ofmethods of producing colored contact lenses are described in U.S. Pat.Nos. 3,679,504 to Wichterle, 5,018,849 to Su et al., 5,302,978 to Evanset al., 5,120,121 to Rawlings et al., and 5,166,122 to Rawlings, andEuropean Patent Publication No. 0 472 496 A2. Contact lenses thatcontain UV-absorbers are known in the art. As an example, one can usethe UV-absorber disclosed in U.S. Pat. No. 5,637,726 to Collins et al.,in the amounts disclosed.

For a clear lens, it is preferred to use violet colorant in an amountbetween about 0.0001% and about 0.01% on a dry weight (before lens ishydrated and before diluent and/or saline is added) basis to mask theyellow tint. More preferably, between about 0.002% and about 0.009% isused.

For a colored lens, it is preferred to use violet colorant in an amountbetween about 0.0001% and about 0.01% on a dry weight basis to mask theyellow tint. More preferably, between about 0.004% and about 0.009% isused.

Of course, the exact amount depends on the strength of the yellow tintotherwise present from the UV absorber added to the lens, and the typeof violet colorant used to mask the yellow tint. Carbazole violet, andPigment Violet Nos. 1, 14, 15 16, 19 and 32 are examples of just a fewviolet colorants that may be useful in the present invention. Thesepigments can be used in combination. Also, a dispersion containing blueand red pigments may be made and added to the monomer mixture.

In addition, up to about 0.003 wt % (dry weight basis) of a handlingtint, such as phthalocyanine green and the like, more preferably about0.002 wt %, may be used in combination with the violet colorant,depending on the tint level desired and the amount of yellow tint to bemasked.

EXAMPLES Example 1

Colored contact lenses were made according to the followingformulations:

TABLE 1 A B Ingredient (Solids) (Total) (Solids) HEMA 86.44% 49.62%85.70% EOEMA 9.81 4.97 8.58 EDMA 1.20 2.07 MAA 1.80 0.81 1.40 BZT***1.50 0.82 1.42 Carbazole 0.40* 0.20** 0.35** Violet Vazo 52 0.05 0.280.48 IPA — 42.10 — Total 100.00% 100.00% 100.00% *A 1/99 w/w dispersionof carbazole violet in HEMA **A 2.5/97.5 w/w dispersion of carbazoleviolet in HEMA ***UV absorber:2-(2′-hydroxy-3′-tert-butyl-5′-(3″-(4″′-vinylbenzoxy)propoxy)phenyl)-5-methoxy-2H-benzotrizole

Example 2

Colored contact lenses were also made according to the followingformulations:

TABLE 2 A Ingredient (Total) (Solids) HEMA 49.491% 85.476% EOEMA 4.978.584 EDMA 1.20 2.073 MAA 1.059 1.829 BZT** 0.82 1.416 Carbazole 0.080*0.138* Violet Vazo 52 0.28 0.484 IPA 42.10 — Total 100.00% 100.00% *A2.5/97.5 w/w dispersion of carbazole violet in HEMA **UV absorber:2-(2′-hydroxy-3′-tert-butyl-5′-(3″-(4″′-vinylbenzoxy)propoxy)phenyl)-5-methoxy-2H-benzotrizole

Example 3 Contact lenses with a handling tint may be made according tothe following formulations:

TABLE 3 A B Ingredient (Solids) (Total) (Solids) HEMA 86.41% 49.57%85.62% EOEMA 9.81 4.97 8.58 EDMA — 1.20 2.07 MAA 1.80 0.81 1.40 BZT***1.50 0.82 1.42 Carbazole Violet 0.40* 0.23* 0.40* Phthalocyanine 0.03**0.02** 0.03** Green Vazo 52 0.05 0.28 0.48 IPA — 42.10 — Total 100.00%100.00% 100.00% *A 1/99 w/w dispersion of carbazole violet in HEMA **A6.98/93.02 w/w dispersion of phthalocyanine green in HEMA ***UVabsorber:2-(2′-hydroxy-3′-tert-butyl-5′-(3″-(4″′-vinylbenzoxy)propoxy)phenyl)-5-methoxy-2H-benzotrizole

Example 4

Clear lenses may be made according to the following formulations:

TABLE 4 Ingredient A HEMA 52.786% EOEMA 5.727 Carbazole 0.200* VioletIPA 37.00 EDMA 1.618 MAA 1.057 Vazo-52 ™ 0.336 Lupersol- 0.331 256 ™UV-Absorber 0.945 TOTAL 100.00% *A 1/99 w/w dispersion of carbazoleviolet in HEMA

Example 5

Colored lenses may be made by applying the modifying colors to thecontact lenses made according to Examples 1 and 2 by using any knownmethod. One such method is disclosed in U.S. Pat. No. 4,582,402, toKnapp. Typically, the modifying colors cover between about 15% and about50% of the lens portion covering the wearer's iris. The carbazole violetin the lens masks the yellowish tint otherwise present from theUV-absorber so as to not affect the cosmetic appearances of the modifiedcolor of the eye.

Formulations of the most preferred ink pastes for the modifying colorsare:

TABLE 5 Color Ingredient Green Blue Aqua Violet Ethyl Lactate 31.35% 22.50%  22.50%  22.50%  Polymer Soln. 65.33%  76.00%  76.01%  76.00% PCN Blue  —% 1.50% 0.29%  —% PCN Green 0.90%  —% 1.20%  —% Carbazole  —%  — %  — % 1.50% Violet Hydrophobic 2.42%  — %  — %  — FeO Total100.00%  100.00%  100.00%  100.00% 

To produce the preferred ink paste, the ingredients are mixed in agrinding media. For 651 gram and 3000 gram samples of ink paste, 850grams and 4298 grams of grinding media are used, respectively. Thetarget viscosity of the polymer solutions are about 35,000 CPS for eachformulation, except for the green color which has a target viscosity ofabout 50,000 CPS. The polymer solutions are known in the art, and mayalso include binding polymers to fix the color to the contact lenses.

Results

An internal focus study demonstrated that a UV-absorbing clear lens thatcontained the violet tint, such as made according to example No. 1,achieved 100% concordance with existing acceptable products.

The described embodiments are to be considered in all respects only asillustrative and not restrictive, and the scope of the invention,therefore, is indicated by the appended claims rather than by theforegoing description. All changes that come within the meaning andrange of equivalency of the claims are to be embraced within theirscope.

I claim:
 1. A clear contact lens comprising: a) a UV absorbing compoundpresent in an amount greater than about 0.9 wt % dry basis sufficient tocause a noticeable yellow tint in a conventional clear contact lens, andb) an amount of violet colorant greater than about 0.0001 wt % dry basissufficient to mask the yellow tint so as to make the color of the lenscosmetically indistinguishable from a clear contact lens without said UVabsorbing compound.
 2. The lens of claim 1, wherein the violet colorantis carbazole violet.
 3. The lens of claim 1 having between about 0.0001wt % and about 0.01 wt % dry basis violet colorant.
 4. The lens of claim3 having between about 0.002 and 0.009 wt % dry basis violet colorant.5. The lens of claim 1 having at least about 1 wt % dry basisUV-absorbing compound.
 6. A tinted contact lens comprising a handlingtint, in an amount less than 0.003 wt % dry basis, a UV-absorbingcompound in an amount greater than about 0.09 wt % dry basis that wouldbe sufficient to cause a noticeable yellow tint, and an amount of violetcolorant greater than about 0.0001 wt % dry basis sufficient to mask theyellow tint otherwise caused by the presence of the UV-absorbingcompound.
 7. The lens of claim 6, wherein the violet colorant iscarbazole violet.
 8. The lens of claim 6 having between about 0.0001 wt% and about 0.01 wt % dry basis violet colorant.
 9. The lens of claim 8having between about 0.004 and about 0.009 wt % dry basis violetcolorant.
 10. The lens of claim 6 further comprising at least about 1 wt% dry basis UV-absorbing compound.